The Collaborative International Dictionary of English v.0.48:

Hogframe \Hog"frame`\, n. (Steam Vessels)
   A trussed frame extending fore and aft, usually above deck,
   and intended to increase the longitudinal strength and
   stiffness. Used chiefly in American river and lake steamers.
   Called also hogging frame, and hogback.
   [1913 Webster]